Heretofore, as vehicle seat reclining devices, there has been known one which, as shown in Patent Document 1, is provided with a lower arm (20) attached on the seat cushion side and securing an internal gear (32) thereto, an upper arm (10) attached on the seatback side and securing thereto an external gear (31) which is fewer in number of teeth than the internal gear (32), a pair of wedge members (35, 36) frictionally engageable with, and frictionally disengageable from, the lower arm (20) or the upper arm (10), a spring (37) arranged between the pair of wedge members (35, 36) and urging one of the wedge members (35, 36) at all times in a direction for friction engagement, and a drive shaft (33) for moving one of the wedge members (35, 36) in a direction to release the friction engagement against the resilient force of the spring (37) to rotate the wedge members (35, 36) relative to the lower arm (20) or the upper arm (10) through the spring (37). When the drive shaft (33) is rotated, one of the wedge members (35 for example) is pushed against the resilient force of the spring, and the other wedge member (36 for example) is also pushed through the spring. Then, the wedge members (35, 36) are both rotated relative to the lower arm (20) or the upper arm (10) to successively move the meshing position of the external gear (31) on the upper arm (10) relative to the internal gear (32) on the lower arm (20). As a result, the upper arm (10) is turned relative to the lower arm (20) in dependence on the difference in number of teeth between the external gear (31) and the internal gear (32), whereby the angle of the upper arm (10) relative to the lower arm (20) is adjusted.
Here, when the drive shaft (33) is rotated, the rotational torque of the drive shaft (33) is transmitted in the order of the driving side wedge member (35 for example), the spring (37) and the driven side wedge member (36 for example). When pushed by the spring (37), the driven side wedge member (36 for example) is rotated by being sandwiched between an internal surface of a bushing (34) secured to the internal gear (32) and an external surface of a cylindrical portion (31f) of the external gear (31). Thus, it may occur that the frictional resistance which the wedge members suffer from the internal surface of the busing (34) or the external surface of the cylindrical portion (31f) abruptly changes due to the gear accuracy or an external force. In this case, a momentary movement (skip) takes place on the wedge member (36 for example) when the same is released from the frictional resistance, so that the angle adjustment of the seatback is liable to be prevented from being carried out smoothly. To avoid this, in the Patent Document 1, it is proposed to suppress the occurrence of the skip of the wedge member on the driven side by bringing an elastic member (40) made of rubber into contact with the wedge member (36 for example) on the driven side to reduce the moving speed of the wedge member (36 for example) on the driven side.    Patent Document 1: JP2006-334284 A1 (refer to Claim 1 and paragraphs [0026] to [0048])